Underwater television observations on the intertidal movements of shore crabs,Carcinus maenas, across a mudflat

Publisher Website
Google Scholar
Abstract
Closed circuit underwater television observations showed that, in summer, large numbers ofCarcinus maenasperformed daytime tidal migrations up and down a small mudflat in the Menai Strait, North Wales. At the observation point, 25 m above mean low water mark of spring tides, numbers of crabs moving upshore on flood tides averaged 84 m—1of tideline, ranging from 48 to 126 m—1. Most crabs were of 20–50 mm carapace width (1 and 11 groups); none smaller than 15 mm was seen. Peak movements occurred in at least 0.5 m depth of water. Over the high tide period, most crabs were dispersed over the upper half of the mudflat where crab population densities of 1·8–2·5 m—2were indicated by diving observations.